With respect to the material used for vehicle interiors, single layer construction resin sheets made with polyvinyl chloride or thermoplastic polyolefin resins (TPO) are frequently used for surface materials for instrument panels/dashboards. The brightness of the resin sheets is low (60 or less) to prevent reflection on the windshield. The surface of an instrument panel/dashboard, which has resin sheets like these, absorbs the incoming rays of the sun which come in through the windshield and becomes very hot.
It is well known that the interior of a parked automobile gets very hot in the blazing sun. According to measurement of the temperature of automobile interiors in the summer in Japan, the temperature inside automobiles parked in the sun reaches approximately 70° C. As for the materials used in the interior, it is reported that the top of dashboards reach about 100° C. while the surface of the ceiling materials and the surface of seats reach high temperatures of around 70° C. Needless to say riding in a vehicle under these circumstances is unpleasant and not only does the passenger feel uncomfortable because the heat is radiated for a long time from the materials used in the interior of the vehicle, the seat feels hot to the passenger due to thermal conductivity from the heat accumulated in the surface of the seat. In addition, the temperature inside of the vehicle and the temperature of the materials used in the interior of the vehicle do not go down readily with ventilation or from air conditioning so that excessive consumption of energy due to air conditioning becomes a problem.
Hitherto, interior material surfaces have been made to include infrared ray reflecting pigments and technology which reflects infrared rays has been proposed concerning problems like these of parked cars in the sun for the purpose of preventing excessive heating of the surfaces of interior materials. See Japanese Unexamined Patent Application Publication No. 2001-114149 (EP 1 179 628 A1) and Japanese Unexamined Patent Application Publication No. 2001-122044.
However, with these technologies, the direction of reflection becomes irregular and most of the reflected light rays are absorbed in the resin layer and are converted to heat because the infrared reflecting pigment powder is mixed into the resin randomly. Moreover, approximately half of the energy of the sun's rays is visible light and in addition to that, the major cause of rising temperatures of the surface of vehicle interiors has been visible light because the window glass used in automobiles in recent years has been predominantly thermally insulated glass which absorbs near infrared. Thus, a significant effect in preventing the excessive heating of surfaces of automobile interiors cannot be expected from interior facing materials which reflect infrared rays.
Likewise, an optical reflecting feature has been tried on a vehicle other than reflection by surfaces of interior materials. Specifically, a technology is known which concerns multi-layered glass for vehicles which adds a reflecting feature to the glass of windows so that ultra-violet rays are prevented from entering the interior of a vehicle. See Japanese Patent No. 3315453.
However, windshield and front and side windows must have a visible light transmission rate (Tv) of at least 70% according to most laws. In order to maintain this standard, a reflecting feature can only have a sunlight reflection rate (Re) of 20 to 30% and one cannot hope for an increase in performance beyond this. As pathways of entry for light, the windshield and front and side windows have a large area and the fact that no more can be done with these windows for measures of keeping temperatures down means that it is necessary to devise other measures for controlling temperatures. Incidentally, the values of sunlight reflection rate (Re), sunlight transmission rate (Te), visible light reflection rate (Rv) and visible light transmission rate (Tv) cited earlier are measured according to Japan Industrial Standard (JIS) R3106.
Measures for controlling temperatures by means other than mentioned above might include methods of increasing the rate of reflection or the brightness of the surface interior materials and reflecting the energy of the sun's rays for the purpose of preventing excessive heating of the surfaces of interior materials. However, merely raising the rate of reflection of visible light (Rv) of the surface of interior materials would radiate it towards other parts of the interior and ultimately would result in an increase in temperatures inside a vehicle as before. In addition, there is a concern that due to the angle of the reflected sunlight, the reflected light would get into the driver's eyes, or the interior materials would be reflected in the glass of the windows causing a glare that would obstruct the driver's field of vision. Thus, raising the rate of reflection and suppressing window reflection and glare for the driver are in a paradoxical relationship so that the achievement of materials and configuration which prevent window reflection and driver glare without diminution of the reflecting feature is required.